1. Field of the Invention
The present invention relates to a method of manufacturing components for a tyre for vehicle wheels, of the type comprising the steps of: a) feeding an elongated element from a delivery member disposed adjacent to an outer surface of a toroidal support; b) giving the toroidal support a rotatory motion for circumferential distribution around a geometric axis of rotation thereof, so that the elongated element is circumferentially distributed onto the toroidal support; c) carrying out controlled relative displacements between the toroidal support and the extrusion die so as to form with said elongated element, a plurality of coils disposed mutually in side by side relationship in order to define a tyre component.
The invention also relates to an apparatus for manufacturing components for a tyre being worked, of the type comprising: a toroidal support arranged for carrying the components of a tyre being worked; feeding devices or other convenient feeder means for feeding at least one elongated element through a delivery member disposed adjacent to an outer surface of the toroidal support; circumferential-distribution devices or other convenient circumferential-distribution means arranged to drive the toroidal support in rotation around a geometric axis thereof, so that said elongated element is circumferentially distributed onto the toroidal support itself; transverse-distribution devices or other convenient transverse-distribution means arranged to give a relative movement between the toroidal support and said delivery member, for distributing said elongated element so as to form a plurality of coils disposed in side by side relationship in order to define a tyre component.
2. Description of the Related Art
Manufacturing of tyres for vehicle wheels involves formation of a carcass structure essentially consisting of one or more carcass plies having a substantially toroidal configuration and the axially opposite side edges of which are connected to respective circumferentially-inextensible annular reinforcing elements, usually named “bead cores”.
Applied to the carcass structure, at a radially outer position thereof, is a belt structure comprising one or more belt strips in the form of a closed ring, essentially made up of textile or metallic cords suitably oriented in respect of each other and of the cords belonging to the adjacent carcass plies.
At a radially outer position relative to the belt structure, a tread band is then applied which usually consists of a strip of elastomer material of suitable thickness.
It is to point out that, to the purposes of the present description, by the term “elastomer material” it is intended the rubber blend in its entirety, that is the bled formed of at least one base polymer suitably amalgamated with reinforcing fillers and process additives of various types.
Ultimately, on the opposite sides of the tyre being manufactured, a pair of sidewalls is applied, each of which covers one side portion of the tyre included between a so-called shoulder region, located close to the corresponding side edge of the tread band, and a so-called bead located at the corresponding bead core.
Traditional production methods essentially provide that the above listed tyre components should be first made separately of each other, to be then assembled in a tyre-manufacturing step.
The Applicant's present trend is however that of resorting to production methodologies enabling production and stocking of semi-finished products to be minimized or, possibly, eliminated.
Practically, the Applicant's research and development are oriented towards new process solutions enable to manufacture the individual components applying them directly to the tyre being manufactured according to a preestablished sequence.
On the other hand, from U.S. Pat. No. 5,453,140 it is known a method and an apparatus forming a carcass ply by laying down a plurality of parallel cords disposed circumferentially in side by side relationship onto a rigid toroidal support the shape of which matches that of the tyre to be obtained, which cords are drawn from a continuous cord sequentially cut into lengths of appropriate size.
The Applicant too has developed manufacturing methods for forming a carcass structure, in which the carcass plies are obtained by laying down onto a rigid toroidal support, strip-like lengths obtained by sequentially cutting a continuous element made up of several cords incorporated into a layer of elastomer material.
Within the manufacturing scope of the carcass structure, as well as of other structural tyre components such as sidewalls and tread band for example, manufacturing processes have been also proposed which aim at obtaining the desired component by laying down onto the tyre being worked, a continuous strip-like element of elastomer material of a reduced section relative to that of the component to be obtained, and such arranged as to form a plurality of coils disposed consecutively in side by side and/or overlapped relationship around the rotation axis of the tyre, so as to define the component itself in its final configuration.
In more detail, in U.S. Pat. Nos. 4,963,207 and 5,171,394 a method and an apparatus are respectively described in which given tyre components are obtained by laying down a strip-like element of elastomer material onto a rigid toroidal support, which strip-like element is continuously fed from a delivery member associated with a volumetric extruder.
While the toroidal support is rotated around its own geometric axis, giving rise to a circumferential distribution of the strip-like element, the volumetric extruder is moved so as to impart controlled displacements to the delivery member in a meridian plane of the toroidal support, in order to distribute the different coils formed by the continuous strip-like element according to a predetermined pattern.
In U.S. Pat. No. 5,221,406 it is provided that a plurality of volumetric extruders should be arranged around the toroidal support, each of them being adapted to feed, through its own delivery member, a respective continuous strip-like element to be selectively employed for making a given tyre component.